1. Field of the Invention
The present invention relates to an image apparatus and an evaluation method.
2. Discussion of the Background
There is known an autofocusing system having an autofocusing (AF) function of detecting defocus amounts of a photographic lens in a plurality of focus detection areas set within a shooting screen and driving the photographic lens to an in-focus position based on the defocus amount in any one of the focus detection areas, and an image tracking function of storing an image of a subject (an object), which is included in a captured image and is to be tracked, as a template image (reference image) and tracking the object, i.e., the tracking target, while performing a search to find a position of an image, which is the same as or similar to the template image, in repeatedly captured images, wherein the focus detection area at an in-screen position obtained by an image tracking result is selected and the photographic lens is driven to an in-focus position based on the defocus amount in the selected focus detection area. Japanese Unexamined Patent Application Publication No. 2005-215040 discloses such an autofocusing system. The contents of this publication are incorporated herein by reference in their entirety.
However, when a photographer instructs the start of tracking of a shooting target, a photographic lens is not always focused at a target object. In the case of a lens having a long focal length, for example, if there is just a slight difference between a setting distance set by a range ring for the lens and an actual shooting distance, the shooting target is photographed in a substantially blurred state. When the tracking is started in such a state, a blurred image of the shooting target is employed as the template image. As a result, the target object is lost during the tracking, or an object other than the target is falsely recognized as the tracking target, whereby tracking performance deteriorates.